Rubber composition for tire and winter tire using the same

ABSTRACT

A rubber composition for a tire, which does not require the addition of a compound when synthesizing rubber component and the modification of a rubber component, and a winter tire using the rubber composition are provided. The rubber composition for a tire contains fine particles of rotaxane having a straight chain molecule, acyclic molecule clathrating the straight chain molecule and blocking groups arranged at both terminals of the straight chain molecule such that the cyclic molecule does not desorb from the straight chain molecule, covered with silica; a rubber component comprising styrene-butadiene rubber; and at least one of carbon black and silica, wherein the total content of the fine particles, the carbon black and the silica (excluding silica covering rotaxane) is 70 to 150 parts by mass per 100 parts by mass of the rubber component.

TECHNICAL FIELD

The present invention relates to a rubber composition for a tire, and awinter tire using the rubber composition.

BACKGROUND ART

A winter tire is required to have braking performance (snow performance)when running on a snowy road surface. Improvement in flexibility at lowtemperature is required in a rubber composition in order to improvebraking performance on a snowy road surface. On the other hand, aproblem occurs such that when flexibility is improved, reinforcingproperty is deteriorated.

SUMMARY OF THE INVENTION

The present inventors have reached to add rotaxane to a rubbercomposition as a means for giving flexibility at low temperature to therubber composition.

JP-A-2014-201629 and JP-A-2018-24768 describe a rubber compositionhaving rotaxane added thereto as a rubber composition that is difficultto generate cracks. However, for obtaining the effect of rotaxane, therotaxane had to be added when synthesizing a rubber component(polymerization stage) or a rubber component or a cyclic molecule ofrotaxane had to be modified, in order to bond the rubber components torotaxane.

In view of the above, an object of the present invention is to provide arubber composition for a tire, which does not require the addition of acompound when synthesizing rubber component and the modification of arubber component, and can improve snow performance while maintainingreinforcing property as compared with the conventional rubbercomposition for a tire, having only the general carbon black and silicaas reinforcing filler added thereto, and a winter tire using the rubbercomposition.

To overcome the above problems, a rubber composition for a tireaccording to one embodiment of the present invention contains fineparticles of rotaxane having a straight chain molecule, a cyclicmolecule clathrating the straight chain molecule and blocking groupsarranged at both terminals of the straight chain molecule such that thecyclic molecule does not desorb from the straight chain molecule,covered with silica, a rubber component comprising styrene-butadienerubber, and at least one of carbon black and silica, wherein the totalcontent of the fine particles, the carbon black and the silica(excluding silica covering rotaxane) is 70 to 150 parts by mass per 100parts by mass of the rubber component.

The rotaxane may have a modifying group by caprolactone in the cyclicmolecule.

The fine particles may have an average particle diameter of 1 to 50 μm.

The content of the fine particles may be 10 to 100 parts by mass per 100parts by mass of the rubber components.

The content of the rotaxane may be 9.8 to 98 parts by mass per 100 partsby mass of the rubber components.

A winter tire according to one embodiment of the present invention usesthe rubber composition in a tread part.

According to the rubber composition for a tire of the present invention,a pneumatic tire having improved snow performance while maintainingreinforcing property as compared with the conventional rubbercomposition for a tire can be obtained. Furthermore, the effect ofrotaxane is obtained by adding fine particles of rotaxane covered withsilica to an unvulcanized rubber as with other additives. As a result,the rotaxane is not required to be added during synthesis of the rubbercomponents, and the rubber component is not required to be modified.

DETAILED DESCRIPTION OF THE INVENTION

Elements in the embodiment for carrying out the present invention aredescribed in detail below.

The rubber composition for a tire according to the present embodimentcontains fine particles of rotaxane having a straight chain molecule, acyclic molecule clathrating the straight chain molecule and blockinggroups arranged at both terminals of the straight chain molecule suchthat the cyclic molecule does not desorb from the straight chainmolecule, covered with silica, a rubber component comprisingstyrene-butadiene rubber, and at least one of carbon black and silica,wherein the total content of the fine particles, the carbon black andthe silica (excluding silica covering rotaxane) is 70 to 150 parts bymass per 100 parts by mass of the rubber component.

The rubber component according to the present embodiment includesstyrene-butadiene rubber (SBR). However, the rubber component is notlimited to this, and may further include natural rubber (NB), butadienerubber (BR), isoprene rubber (IR), styrene-isoprene copolymer rubber,butadiene-isoprene copolymer rubber, styrene-isoprene-butadienecopolymer rubber, or a modified rubber obtained by modifying a part ofterminals or main chains of those. Styrene-butadiene rubber, naturalrubber and butadiene rubber are preferably used together. Thestyrene-butadiene rubber (SBR) includes modified SBR obtained bymodifying a part of terminals and main chains of those.

When styrene-butadiene rubber, natural rubber and butadiene rubber areused together as the rubber component, the content of thestyrene-butadiene rubber (SBR) in 100 parts by mass of the rubbercomponent is not particularly limited, but is preferably 20 to 70 partsby mass and more preferably 30 to 60 parts by mass. The content of thenatural rubber in 100 parts by mass of the rubber component is notparticularly limited, but is preferably 20 to 60 parts by mass and morepreferably 30 to 50 parts by mass. The content of the butadiene rubberin 100 parts by mass of the rubber component is not particularlylimited, but is preferably 10 to 40 parts by mass and more preferably 10to 30 parts by mass.

The rotaxane according to the present invention has a straight chainmolecule, a cyclic molecule clathrating the straight chain molecule andblocking groups arranged at both terminals of the straight chainmolecule such that the cyclic molecule does not desorb from the straightchain molecule. In the present description, the term “rotaxane” includespolyrotaxane having two or more cyclic molecules.

The straight chain molecule is not particularly limited, and examplesthereof include polyalkyls, polyesters, polyethers, polyamides,polyacryls and a straight chain molecule having a benzene ring. Thosemay be contained alone and may be contained as mixtures of two or morekinds.

Examples of the polyalkyls include polyethylene, polypropylene,polyisoprene and polybutadiene. The polyesters, polyamides, straightchain molecule having a benzene ring and polyacryls can be commonmaterials generally used.

Examples of the polyethers include polyethylene glycol, and thepolyethylene glycol is suitably used from the standpoint of excellentclathration property of a cyclic molecule.

Weight average molecular weight of the straight chain molecule is notparticularly limited, but is preferably 10,000 to 40,000, morepreferably 15,000 to 35,000 and still more preferably 20,000 to 30,000.

The cyclic molecule is not particularly restricted so long as it has acyclic structure, clathrates a straight chain molecule and produces aslide ring effect described hereinafter. In the present description, the“cyclic structure” is not always necessary to be a closed form. In otherwords, the cyclic molecule may substantially have a cyclic structure,like “C” character.

The cyclic molecule preferably has a reaction group. This facilitates toobtain interaction with silica and further facilitates to introduce amodifying group or the like. Examples of such a reaction group include ahydroxyl group, a carboxyl group, an amino group, an epoxy group, anisocyanate group, a thiol group and an aldehyde group, although notlimited to those. The reaction group is preferably a group that does notreact with a blocking group in the case of forming the blocking groupdescribed hereinafter (blocking reaction). Considering this point, thereaction group is preferably a hydroxyl group, an epoxy group or anamino group, and is particularly preferably a hydroxyl group.

Examples of the cyclic molecule specifically include cyclodextrin, crownethers, benzo crowns, dibenzocrowns, dicyclohexanocrowns, and thosederivatives or modified bodies. Of those, cyclodextrin and cyclodextrinderivatives are preferably used. The kind of cyclodextrin andcyclodextrin derivatives is not particularly restricted. Thecyclodextrin may be any of α type, β type, γ type, δ type and ε type.The cyclodextrin derivatives may also be any of α type, β type, γ type,δ type and ε type. The cyclodextrin derivatives intend to be an aminoform, a tosyl form, a methyl form, a propyl form, a monoacetyl form, atriacetyl form, a benzoyl form, a sulfonyl form, a monochlorotriazinylform, and the like. More specific examples of the cyclodextrin andcyclodextrin derivatives that can be used in the present inventioninclude cyclodextrin such as α-cyclodextrin (number of glucose: 6),β-cyclodextrin (number of glucose: 7) or γ-cyclodextrin (number ofglucose: 8); and cyclodextrin derivatives such as dimethyl cyclodextrin,glucosyl cyclodextrin, 2-hydroxypropyl-α-cyclodextrin, 2,6-di-O-methyl-α-cyclodextrin, 6-O-α-maltosyl-α-cyclodextrin,6-O-α-D-glucosyl-α-cyclodextrin, hexakis(2,3,6-tri-O-acetyl)-α-cyclodextrin, hexakis(2,3,6-tri-O-methyl)-α-cyclodextrin, hexakis(6-O-tosyl)-α-cyclodextrin,hexakis(6-amino-6-deoxy)-α-cyclodextrin,hexakis(2,3-acetyl-6-bromo-6-deoxy)-α-cyclodextrin,hexakis(2,3,6-tri-O-octyl)-α-cyclodextrin,mono(2-O-phosphoryl)-α-cyclodextrin, mono[2,(3)-O-(carboxymethyl)]-α-cyclodextrin,octakis(6-O-t-butyldimethylsilyl)-α-cyclodextrin,succinyl-α-cyclodexrrin, glucuronylglucosyl-β-cyclodextrin,heptakis(2,6-di-O-methyl)-β-cyclodextrin,heptakis(2,6-di-O-ethyl)-β-cyclodextrin,heptakis(6-O-sulfo)-β-cyclodextrin,heptakis(2,3-di-O-acetyl-6-O-sulfo)-β-cyclodextrin,heptakis(2,3-di-O-methyl-6-O-sulfo)-β-cyclodextrin,heptakis(2,3,6-tri-O-acetyl)-β-cyclodextrin,heptakis(2,3,6-tri-O-benzoyl)-β-cyclodextrin,heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin,heptakis(3-O-acetyl-2,6-di-O-methyl)-β-cyclodextrin,heptakis(2,3-O-acetyl-6-bromo-6-deoxy)-β-cyclodextrin,2-hydroxyethyl-β-cyclodextrin, hydroxypropyl-β-cyclodextrin,2-hydroxypropyl-β-cyclodextrin,(2-hydroxy-3-N,N,N-trimethylamino)propyl-β-cyclodextrin,6-O-α-maltosyl-β-cyclodextrin, methyl-β-cyclodextrin,hexakis(6-amino-6-deoxy)-β-cyclodextrin,bis(6-azido-6-deoxy)-β-cyclodextrin,mono(2-O-phosphoryl)-β-cyclodextrin,hexakis[6-deoxy-6-(1-imidazolyl)]-β-cyclodextrin,monoacetyl-β-cyclodextrin, triacetyl-β-cyclodextrin,monochlorotriazinyl-β-cyclodextrin, 6-O-α-D-glucosyl-β-cyclodextrin,6-O-α-D-mantosyl-β-cyclodextrin, succinyl-β-cyclodextrin,sccinyl-(2-hydroxypropyl)-β-cyclodextrin,2-carboxymethyl-β-cyclodextrin, 2-carboxyethyl-β-cyclodextrin,butyl-β-cyclodextrin, sulfopropyl-β-cyclodextrin,6-monodeoxy-6-monoamino-β-cyclodextrin,silyl[(6-O-t-butyldimethyl)-2,3-di-O-acetyl]-β-cyclodextrin,2-hydroxyethyl-γ-cyclodextrin, 2-hydroxypropyl-γ-cyclodextrin,butyl-γ-cyclodextrin, 3A-amino-3A-deoxy-(2AS, 3AS)-γ-cyclodextrin,mono-2-O-(p-toluenesulfonyl)-γ-cyclodextrin,mono-6-O-(p-toluenesulfonyl)-γ-cyclodextrin,mono-6-O-mesitylenesulfonyl-γ-cyclodextrin,octakis(2,3,6-tri-O-methyl)-γ-cyclodextrin,octakis(2,6-di-O-phenyl)-γ-cyclodextrin,octakis(6-O-t-butyldimethylsilyl)-γ-cyclodextrin andoctakis(2,3,6-tri-O-acetyl)-γ-cyclodextrin. The cyclic molecules ofcyclodextrin or the like described above can be used alone or asmixtures of two or more kinds. Of the cyclic molecules, α-cyclodextrin,β-cyclodextrin, γ-cyclodextrin, and their derivatives are preferred, andα-cyclodextrin and their derivatives are particularly preferably usedfrom the standpoint of clathration.

The blocking group is not particularly limited so long as it is a groupthat is arranged at both terminals of the straight chain molecule andcan hold the state that the cyclic molecule clathrates the straightchain molecule.

Examples of the group include a group having “bulkiness” and a grouphaving “ionicity”. The term “group” used herein means various groupsincluding a molecule group and high molecule group. Examples of thegroup having “bulkiness” include a spherical group and a sidewall-shaped group.

The ionicity of a group having “ionicity” and the ionicity of the cyclicmolecule have influence on each other. For example, repulsion of thoseeach other can hold the state that the cyclic molecule has been skeweredwith the straight chain molecule.

Specific examples of the blocking group include dinitrophenyl groupssuch as 2,4-dinitrophenyl group and 3,5-dinitrophenyl group,cyclodextrin groups, adamantane groups, trityl groups, fluoresceingroups, pyrene groups, and their derivatives or modified compounds.

The rotaxane may be that the cyclic molecule has a modifying group, andthe example thereof includes modified rotaxane having (—CO(CH₂)₅OH)group as a modifying group by caprolactone. Specifically, the rotaxaneis rotaxane having (—CO(CH₂)₅OH) group, wherein the cyclic molecule iscyclodextrin, a part or the whole of hydroxyl groups of the cyclodextrinis modified with a modifying group and the modifying group is amodifying group by caprolactone. More specifically, the rotaxane isrotaxane having (—CO(CH₂)₅OH) group that is a modifying group bycaprolactone and bonds to a —O—C₃H₅—O— group of the cyclic molecule.

The fine particles of rotaxane covered with silica used in the presentinvention are that at least apart of the surface of the rotaxane iscovered with silica and the rotaxane and the silica are chemicallybonded to each other.

As the fine particles of rotaxane covered with silica, commerciallyavailable products can be used. Examples of the commercially availableproducts specifically include SH2400B-0501 and SH2400B-2001 manufacturedby Advanced Soft Materials.

The content of the fine particles is preferably 10 to 100 parts by mass,more preferably 20 to 90 parts by mass and still more preferably 20 to80 parts by mass, per 100 parts by mass of the rubber component.

The content of the rotaxane is preferably 9.8 to 98 parts by mass, morepreferably 19.6 to 88.2 parts by mass and still more preferably 19.6 to78.4 parts by mass, per 100 parts by mass of the rubber component.

The average particle diameter of the fine particles is not particularlylimited, but is preferably 1 to 50 μm, more preferably 1 to 30 μm andstill more preferably 1 to 20 μm. When the average particle diameter ofthe fine particles is in the above range, the effect by the rotaxane iseasy to be obtained. In the present description, the average particlediameter means a particle diameter in cumulative value 90% (90% volumeparticle diameter (D90)) in particle size distribution (volume basis)obtained by measuring by a laser diffraction/scattering method using alaser diffraction particle size analyzer “SALD-2200” manufactured byShimadzu Corporation and a red semiconductor laser (wavelength 680 nm)as a light source.

The rubber composition according to the present embodiment contains atleast one of carbon black and silica as an inorganic filler. In otherwords, the inorganic filler used may be carbon black alone, may besilica alone or may be a mixture of carbon black and silica. In the casewhere silica is added, apart from the fine particles, the silica doesnot chemically bond to rotaxane and disperses in the rubber composition,apart from the fine particles. Therefore, the silica added can bedistinguished from the silica covering the rotaxane.

The total content of the fine particles, the carbon black and the silica(excluding silica covering rotaxane) is 70 to 150 parts by mass,preferably 80 to 140 parts by mass and more preferably 80 to 120 partsby mass, per 100 parts by mass of the rubber component. The totalcontent of the fine particles, the carbon black and the silica(excluding silica covering rotaxane) can be paraphrased as the totalcontent of the rotaxane, the carbon black and the silica (includingsilica covering rotaxane). When the total content of the fine particles,the carbon black and the silica (excluding silica covering rotaxane) isin the above range, the improvement effect in snow performance is easyto be obtained while maintaining reinforcing property.

The carbon black is not particularly limited and its conventionalvarious kinds can be used. The content of the carbon black is preferably5 to 30 parts by mass, more preferably 5 to 20 parts by mass and stillmore preferably 5 to 15 parts by mass, per 100 parts by mass of therubber component.

The silica is not particularly limited, and wet silica such as wetprecipitated silica or wet gelled silica is preferably used. The contentof the silica (including silica covering rotaxane) is preferably 10 to90 parts by mass and more preferably 10 to 80 parts by mass, per 100parts by mass of the rubber component from the standpoints of thebalance of tan δ of a rubber and reinforcing property.

The rubber composition according to the present embodiment achievesexcellent snow performance while maintaining reinforcing property ascompared with the conventional rubber composition for a tire, by addingthe fine particles of rotaxane covered with silica and at least one ofcarbon black and silica so as to be predetermined contents. Themechanism is not sure, but it is assumed as follows. Slippage occursbetween the cyclic molecule of the rotaxane and the straight chainmolecule thereof when stretching the rubber, by chemical interactionbetween the silica on the surface of the cyclic molecule of the rotaxaneand the rubber component (hereinafter referred to as slide ring effect).The rubber is well stretched even by small stress by the slide ringeffect. As a result, it is considered that flexibility of the rubbercomposition is improved and this contributes to snow performance.Furthermore, the silica on the surface of the fine particles functionsas a reinforcing filler. It is therefore considered that the reinforcingproperty can be maintained by setting the total amount of the fineparticles, the carbon black and the silica to a predetermined content.

Use of the fine particles can bond the rotaxane and the rubber componentthrough the silica on the surface of the fine particles. As a result,the fine particles can be added to unvulcanized rubber as same as inother additives, the addition of the rotaxane when synthesizing therubber component is not required and the modification of the rubbercomponent is not required.

The rubber composition according to the present embodiment may furthercontain a silane coupling agent such as sulfide silane ormercaptosilane. The content of the silane coupling agent is preferably 2to 20 parts by mass per 100 parts by mass of the total amount of thefine particles and the silica added as a reinforcing filler.

In addition to the components described above, compounding chemicalsthat are generally used in rubber industries, such as a process oil,zinc oxide, stearic acid, a softener, a plasticizer, a wax, an ageresister, a vulcanizing agent and a vulcanization accelerator, can beappropriately added to the rubber composition according to the presentembodiment in a general range.

Examples of the vulcanizing agent include sulfur components such aspowdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfurand highly dispersible sulfur. The content of the vulcanizing agent ispreferably 0.1 to 10 parts by mass and more preferably 0.5 to 5 parts bymass, per 100 parts by mass of the rubber component. The content of thevulcanization accelerator is preferably 0.1 to 7 parts by mass and morepreferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubbercomponent.

The rubber composition according to the present embodiment can beproduced by kneading the necessary components according to theconventional method using a mixing machine which is usually used, suchas Banbury mixer, a kneader or rolls. Specifically, the rubbercomposition can be prepared by adding other additives excluding avulcanizing agent and a vulcanization accelerator to a rubber componenttogether with the fine particles of rotaxane covered with silica,followed by mixing, in a first step and adding a vulcanizing agent and avulcanization accelerator to the mixture obtained, followed by mixing,in a final step.

The rubber composition thus obtained can be applied to a tread part, asidewall part and the like of pneumatic tires of various sizes forvarious uses, such as tires for passenger cars, large-sized tires fortrucks, buses and the like, and can be applied to a tread part in apreferred embodiment. The rubber composition can manufacture a pneumatictire according to the conventional method, by, for example, forming therubber composition into a predetermined shape by extrusion processing,combining the formed product with other parts, and then vulcanizationmolding the resulting assembly at, for example, 130 to 190° C.

The kind of the pneumatic tire according to the present embodiment isnot particularly limited, and examples of the pneumatic tire includevarious tires such as tires for passenger cars and tires for heavy loadused in trucks and buses, as described above.

EXAMPLES

Examples of the present invention are described below, but the presentinvention is not construed as being limited to those examples.

Banbury mixer was used. Components excluding a vulcanization acceleratorand sulfur were added and mixed according to the formulations (parts bymass) shown in Table 1 below in a first step (discharge set temperature:160° C.). A vulcanization accelerator and sulfur were added to and mixedwith the mixture obtained above in a final step (discharge settemperature: 90° C.). Thus, a rubber composition was prepared.

The details of each component in Table 1 are as follows.

Natural rubber: RSS#3

SBR1: TUFDENE 1834 manufactured by Asahi Kasei Corporation

SBR2: HPR340, terminal alkoxyl group and amino group-modifiedsolution-polymerized styrene-butadiene rubber, manufactured by JSRCorporation

BR: BR150B manufactured by Ube Industries Ltd.

Carbon black: SEAST KH manufactured by Tokai Carbon Co., Ltd.

Silica: NIPSIL AQ manufactured by Tosoh Corporation

Fine particle 1: SH2400B-0501 (straight chain molecule: polyethyleneglycol, cyclic molecule: cyclodextrin having modifying group bycaprolactone, blocking group: adamantane group, the surface beingcovered with silica), average particle diameter: 7.4 μm, true specificgravity (He substitution method): 1.18 g/cc, silica content: 2%,manufactured by Advanced Soft Materials

Fine particle 2: SH2400B-2001 (straight chain molecule: polyethyleneglycol, cyclic molecule: cyclodextrin having modifying group bycaprolactone, blocking group: adamantane group, the surface beingcovered with silica), average particle diameter: 20 μm, true specificgravity (He substitution method): 1.16 g/cc, silica content: 2%,manufactured by Advanced Soft Materials

Rotaxane compound: SH3400P (straight chain molecule: polyethyleneglycol, cyclic molecule: cyclodextrin having modifying group bycaprolactone, blocking group: adamantane group, the surface being notcovered with silica), manufactured by Advanced Soft Materials

Silane coupling agent: Si69 manufactured by Evonik Japan

Oil: PROCESS NC140 manufactured by JXTG Nippon Oil & Energy Corporation

Zinc oxide: Zinc Oxide #2 manufactured by Mitsui Mining & Smelting Co.,Ltd.

Stearic acid: LUNAC S-20 manufactured by Kao Corporation

Wax: OZOACE 0355 manufactured by Nippon Seiro Co., Ltd.

Age resister: NOCLUC 6C manufactured by Ouchi Shinko Chemical IndustrialCo., Ltd.

Sulfur: POWDERED SULFUR manufactured by Tsurumi Chemical Industry Co.,Ltd.

Vulcanization accelerator: SOXINOL CZ manufactured by Sumitomo ChemicalCo., Ltd.

Hardness and snow performance of each rubber composition obtained wereevaluated using each test piece having a predetermined size obtained byvulcanizing each rubber composition at 160° C. for 30 minutes. Theevaluation methods are as follows.

Hardness: Hardness was measured according to JIS K7215. Hardness wasindicated as an index as the value of Comparative Example 1 that is theformulation of the conventional rubber composition for a tire being 100.Hardness is low as the index is small. It was evaluated that reinforcingproperty was maintained when the index was 95 to 105.

Snow performance: Four test tires were mounted on a passenger car. ABSwas operated from 60 km/hr running on a snowy road and a brakingdistance was measured when speed was reduced to 20 km/hr (average valueof n=10). Inverse number of a braking distance was indicated by an indexas the value of Comparative Example 1 that is the formulation of theconventional rubber composition for a tire being 100. Braking distanceis short as the index is large, and large index indicates excellent snowperformance.

TABLE 1 Com. Com. Com. Com. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 Ex. 3Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Natural rubber 30 30 30 30 3030 30 30 30 30 30 30 30 30 SBR 1 50 50 50 50 50 50 — — 50 50 50 50 50 50SBR 2 — — — — — — 50 50 — — — — — — BR 20 20 20 20 20 20 20 20 20 20 2020 20 20 Carbon black 10 10 — 10 10 10 10 10 10 10 10 10 10 10 Silica 9090 — 70 50 50 50 50 70 70 20 20 60 70 Fine particles 1 — 70 110 — 40 —40 — 20 — 70 — — — Fine particles 2 — — — — — 40 — 40 — 20 — 70 10 40Rotaxane compound — — — 20 — — — — — — — — — — Silane coupling agent 9.016.0 11.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 7.0 11.0 Oil 30 30 30 3030 30 30 30 30 30 30 30 30 30 Zin oxide 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.02.0 2.0 2.0 2.0 2.0 2.0 Stearic acid 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.02.0 2.0 2.0 2.0 2.0 Wax 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.02.0 2.0 Age resister 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.02.0 Sulfur 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0Vulcanization accelerator 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.51.5 1.5 1.5 Total amount of carbon 100 170 110 80 100 100 100 100 100100 100 100 80 120 black, silica and fine particles Hardness 100 130 8084 98 98 98 98 100 100 96 96 95 106 Snow performance 100 70 125 117 110109 109 107 105 106 115 116 120 103

The results obtained are shown in Table 1 above. From the comparisonbetween Comparative Example 1 and Examples 1 to 10, it is seen that whenthe total content of the fine particles, the carbon black and the silica(excluding silica covering rotaxane) is contained in the range of 70 to150 parts by mass per 100 parts by mass of the rubber component,excellent snow performance is obtained while maintaining reinforcingproperty, as compared with the conventional formulation.

From the comparison between Examples 1 to 10 and Comparative Example 2,it is seen that when the total content of the fine particles, the carbonblack and the silica (excluding silica covering rotaxane) exceeds 150parts by mass per 100 parts by mass of the rubber component, reinforcingproperty cannot be maintained and snow performance is poor.

From the comparison between Examples 1 to 10 and Comparative Example 3,it is seen that when the fine particles are contained and the carbonblack and silica are not contained, reinforcing property cannot bemaintained.

From the comparison between Example 6 and Comparative Example 4, it isseen that when the rotaxane compound that is not covered with silica isused, reinforcing property cannot be maintained.

The rubber composition of the present invention can be used in varioustires of passenger cars, light trucks, buses and the like.

What is claimed is:
 1. A rubber composition for a tire, comprising: fineparticles of rotaxane having a straight chain molecule, a cyclicmolecule clathrating the straight chain molecule and blocking groupsarranged at both terminals of the straight chain molecule such that thecyclic molecule does not desorb from the straight chain molecule,covered with silica, a rubber component comprising styrene-butadienerubber, and at least one of carbon black and silica, wherein the totalcontent of the fine particles, the carbon black and the silica(excluding silica covering rotaxane) is 70 to 150 parts by mass per 100parts by mass of the rubber component.
 2. The rubber composition for atire according to claim 1, wherein the rotaxane has a modifying group bycaprolactone in the cyclic molecule.
 3. The rubber composition for atire according to claim 1, wherein the fine particles have an averageparticle diameter of 1 to 50 μm.
 4. The rubber composition for a tireaccording to claim 2, wherein the fine particles have an averageparticle diameter of 1 to 50 μm.
 5. The rubber composition for a tireaccording to claim 1, wherein the content of the fine particles is 10 to100 parts by mass per 100 parts by mass of the rubber component.
 6. Therubber composition for a tire according to claim 2, wherein the contentof the fine particles is 10 to 100 parts by mass per 100 parts by massof the rubber component.
 7. The rubber composition for a tire accordingto claim 3, wherein the content of the fine particles is 10 to 100 partsby mass per 100 parts by mass of the rubber component.
 8. The rubbercomposition for a tire according to claim 4, wherein the content of thefine particles is 10 to 100 parts by mass per 100 parts by mass of therubber component.
 9. The rubber composition for a tire according toclaim 1, wherein the content of the rotaxane is 9.8 to 98 parts by massper 100 parts by mass of the rubber component.
 10. The rubbercomposition for a tire according to claim 2, wherein the content of therotaxane is 9.8 to 98 parts by mass per 100 parts by mass of the rubbercomponent.
 11. The rubber composition for a tire according to claim 3,wherein the content of the rotaxane is 9.8 to 98 parts by mass per 100parts by mass of the rubber component.
 12. The rubber composition for atire according to claim 4, wherein the content of the rotaxane is 9.8 to98 parts by mass per 100 parts by mass of the rubber component.
 13. Therubber composition for a tire according to claim 5, wherein the contentof the rotaxane is 9.8 to 98 parts by mass per 100 parts by mass of therubber component.
 14. The rubber composition for a tire according toclaim 6, wherein the content of the rotaxane is 9.8 to 98 parts by massper 100 parts by mass of the rubber component.
 15. The rubbercomposition for a tire according to claim 7, wherein the content of therotaxane is 9.8 to 98 parts by mass per 100 parts by mass of the rubbercomponent.
 16. The rubber composition for a tire according to claim 8,wherein the content of the rotaxane is 9.8 to 98 parts by mass per 100parts by mass of the rubber component.
 17. A winter tire using therubber composition for a tire according to claim 1 in a tread part.